The specific esterase activity of carboxypeptidase.

It was recently found that the proteolytic enzymes trypsin (19 and chymotrypsin (2) possess specific esterase activity. In addition to catalyzing the hydrolysis of specific peptides (3-7), these enzymes also catalyze the hydrolysis of those esters which possess the structural environment of the specific peptides. In order to substantiate further the suggestion of Schwert et al. (1) that the specific esterase activity is a general attribute of proteolytic enzymes, ester analogues of the specific peptide substrates for carboxypeptidase mere prepared and the influence of the enzyme on these substrates was investigated. Two typical substrates for carboxypeptidase are carbobenzoxyglycyl-L-phenylalanine (8) and chloroacetyl-n-phenylalanine (8, 9). These substrates are enzymatically hydrolyzed to carbobenzoxyglycine and L-phenylalanine in the case of the former substrate, and to chloroacetate and L-phenylalanine in the case of the latter. If carboxypeptidase is endowed with specific esterase activity, the ester analogues of the above substrates, i.e. carbobenzoxyglycyl-P-phenyllactic acid and chloroacetyl-P-phenyllactic acid,l should likewise be hydrolyzed under the influence of carboxypeptidase. The carbobenzoxy group of carbobenzoxyglycyl-n-phenylalanine is required, for it has been shown that carboxypeptidase will not act on substrates which contain a free amino group in close proximity to the susceptible peptide bond (8). However, it may be expected that some